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What Is Chickenpox?

Chickenpox (varicella), a viral illness characterized by a very itchy red rash, is one of the most common infectious diseases of childhood. It is usually mild in children, but adults run the risk of serious complications, such as bacterial pneumonia.

People who have had chickenpox almost always develop lifetime immunity (meaning you can't get it again.) However the virus remains dormant in the body, and it can reactivate later in life and cause shingles.

Because chickenpox can pass from a pregnant woman to her unborn child, possibly causing birth defects, doctors often advise women considering pregnancy to confirm their immunity with a blood test.

What Causes It?

Chickenpox is caused by the herpes zoster virus, also known as the varicella-zoster virus. It is spread by droplets from a sneeze or cough, or by contact with the clothing, bed linens, or oozing vesicles of an infected person. The onset of symptoms is seven to 21 days after exposure. The disease is most contagious a day before the rash appears and up to seven days after, or until the rash forms scabs.